1. Field of the Invention
The invention relates in general to hoist rings and, in particular, to a side mount hoist ring adapted to be mounted on an object to be lifted. The side mount hoist ring is adapted to swivel through a full 360 degrees and pivot through a full 180 degrees, is more economical to fabricate than comparable center mount hoist ring assemblies, and maintains or exceeds the load capacity of a comparable size center mount hoist ring assembly.
2. Description of the Prior Art
Various hoist ring assemblies have been proposed previously. Recently there has been a need to develop hoist ring assemblies that are attachable to objects to be lifted while being able to continuously swivel 360 degrees in one direction and tilt approximately 180 degrees in another. Hoist ring assemblies having these properties have been found very desirable by industry. For example, in Tsui et al U.S. Pat. No. 4,705,422, and Tsui et al U.S. Pat. No. 5,848,815 such swiveling and tilting hoist ring assemblies are disclosed.
It is well known that machining operations on parts are expensive in time and materials. Forgings are much quicker and easier to produce with substantially less waste in material. For hoist ring assemblies having large load carrying capacities, many of the parts must be forged for strength, and then machined to their final dimensions. The prior art assemblies generally require numerous machining operations, and their designs are not readily adaptable for use with "as forged" parts. In particular, the close tolerances generally required in prior configurations could not be made from forgings without several expensive machining operations.
One attempt to solve the problem is Tsui U.S. Pat. No. 5,405,210 where a swiveling and tilting hoist ring assembly is disclosed in which the hoist ring member and retainer member are formed by forging and are assembled in the as forged condition. However, this hoist ring assembly follows the conventional wisdom of making the hoist ring pivot directly on top of the swivel axis. This type of configuration, herein referred to as a center pull hoist ring assembly, requires the shaping of complicated forged parts.
Previous swiveling and pivoting side pull hoist ring assemblies have been proposed. One prior art side pull hoist ring assembly utilizes a large circular ring that pivotally engages an outwardly elongated channel in the main body of the assembly. The size of the elongated channel, starting from its location in the center portion of the body, tapers outwardly to a large size at the end portions of the body in order to allow the circular hoist ring to pivot within the channel. However, due to the manner in which stress is distributed through the circular ring and elongated channel, for a given size, the load capacity of the assembly is significantly less than a comparably sized center pull hoist ring. Thus, this previous swiveling and pivoting side pull hoist ring assembly utilizing a circular hoist ring is undesirably limited to medium load capacities compared to equivalently sized center pull hoist ring assemblies.
Attempts to increase the load capacity of a swiveling and pivoting side mount hoist ring assemblies have also been made. Instead of utilizing a circular hoist ring, a semi-circular hoist ring, or "D" ring, is used. The semi-circular hoist ring has a generally straight segment engaging a U-shaped channel in the body of the assembly. Although, for a given sized assembly, the straight segment and U-shaped channel act to somewhat enhance the load capacity compared to the use of the circular ring, the semi-circular portion of the ring can still undesirably flex, due to bending stresses imposed during lifting. This flexing limits the load capacity of the assembly. Another problem with the previous swiveling and pivoting side mount hoist ring assemblies is that the lift ring is only captively restrained in the assembly when the assembly is mounted to the flat surface of an object. Undesirably, these prior art assemblies rely on the surface of the lifting object to retain the lift ring. Thus, when uninstalled, undesirably, the ring can be misplaced or lost. In addition, due to the swiveling nature of the assembly, the area of the surface of the object must not only be flat, but the area of the flat surface must also be large enough to prevent the ring from escaping from the assembly when swiveling.
Those concerned with these problems recognize the need for an improved simpler, less expensive, and easier to forge, swiveling and tilting side mount hoist ring assembly.
These and other difficulties of the prior art have been overcome according to the present invention.